Electronic – How to check the Electret mic


I recently soldered an electret mic. I have never soldered before. How do
I check whether I have damaged the electret mic? If it was a speaker I could have done continuity check but for a mic I don't know. I measured the resistance it comes somewhere around 1.7Kohm. If I blow into mic ,it
comes to 2Kohm. Is this how we check it?

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I made a pre-amplifier circuit. It's not working. I am not sure whether it is the problem with the mic or the circuit.

Best Answer

Electret mics have a built-in FET as an "amplifier" which requires power.

  • get a power supply, say 5V
  • connect GND to the - of the mic
  • connect 5V to a 22k resistor, the other side of the resistor goes to the mic
  • connect your oscilloscope between GND and the + pin of the mic
  • start whistling, alter two frequencies
  • change input sensitivity on the scope, you shall see a signal in millivolts range
  • and you will see nice sine waves as you're whistling.

Basically this is what you do (without the output capacitor, which cuts the DC power from the output):